The emergence and spread of antimicrobial resistance among ocular pathogens has received widespread attention and raised concern among ocular health practitioners. One particular pathogen that is of special concern is methicillin-resistant Staphylococus aureus (MRSA). There are two types of MRSA, hospital- or healthcare-associated MRSA (HA-MRSA) and community-associated MRSA (CA-MRSA). The difference between the two lies not just on the source of the pathogen, but also in their genetic makeup. HA-MRSA is typically a multidrug-resistant organism, while CA-MRSA isolates are usually susceptible to most non-beta-lactam antimicrobial agents. The percentage of MRSA among clinical Staphylococus aureus isolates was reported to be 16.8% in the United States in 2006 (Asbell et al. Am J Ophthalmol. (2008) 145:951-958). Yet in year 2007 and 2008, the percentage elevated to around 50% (Asbell et al. Ocular TRUST 3: Ongoing Longitudinal Surveillance of Antimicrobial Susceptibility in Ocular Isolates, presented at the 2009 ASCRS Symposium & Congress on Cataract, IOL, and Refractive Surgery; and the ASOA Congress on Ophthalmic Practice Management and Clinical & Surgical Staff Program). The rate is similar to those rates reported in a Taiwanese population (Hsiao et al, Ophthalmology (2012) 119: 522-527). According to data from Ocular TRUST (Tracking Resistance in the U.S. Today, Asbell, et al., 2008), more than 75% of MRSA were considered resistant to various fluoroquinolones such as ciprofloxacin, levofloxacin, gatifloxacin, and moxifloxacin. They have also shown to be resistant to other common antibiotics such as penicillin and tobramycin. Even with the arrival of newer antibiotics such as linezolid, daptomycin, and tigecyline, resistant bacteria still persist. Therefore, there is an urgent need for the development of new antibiotics that could combat these resistant bacteria.
The use of ε-polylysine in contact lens care solutions has been described (see e.g. U.S. Pat. No. 6,187,264, and U.S. Pat. Publ. No. 2005/0074467). Another background application includes co-pending U.S. patent application Ser. No. 14/109,976. This reference and all references are incorporated in their entirety by reference herein.